在flutter中实现无限滚动GridView的最佳实践是什么? [英] What is best practices for implement a infinite scroll GridView in flutter?

问题描述

我想创建一个Gridview来显示将按偏移量从服务器获取的项目.我在GridView中仅加载10个项目，当用户滚动到10个项目后，我将加载更多10个项目.在Flutter中实现Infinite Scroll GridView的最佳实践是什么?谢谢.

I want to create a Gridview that displays items which will be fetching from server by offset. I load only 10 items in GridView, and after user scroll reached to 10, I will load more 10 items. What is the best practice for implement Infinite Scroll GridView in flutter? Thanks.

推荐答案

您需要在ListView和GridView的底部添加ScrollController以进行滚动检测.当您需要GridView时，我创建了ScrollController列表器，并将其添加到GridView's contoller中以检测滚动.我已经创建了它的演示，请检查一次.第一次加载 10 项，当列表位于底部时，它会在其中添加更多 10 项.

You need to add the ScrollController for the scrolling detection at the bottom for the ListView and GridView. As you need the GridView i have created the ScrollController listner and added to the GridView's contollerfor the detection of the scroll. I have created the demo of it , please check it once. At first time it load the 10 items and when list comes to the bottom then it add more 10 items in it.

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

class HomeScreen extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return HomeState();
  }
}

class HomeState extends State<HomeScreen> {
  List dataList = new List<int>();
  bool isLoading = false;
  int pageCount = 1;
  ScrollController _scrollController;

  @override
  void initState() {
    super.initState();

    ////LOADING FIRST  DATA
    addItemIntoLisT(1);

    _scrollController = new ScrollController(initialScrollOffset: 5.0)
      ..addListener(_scrollListener);
  }

  Widget build(BuildContext context) {
    return MaterialApp(
        title: 'Gridview',
        debugShowCheckedModeBanner: false,
        theme: ThemeData(
          primaryColor: Colors.red,
          accentColor: Color(0xFFFEF9EB),
        ),
        home: Scaffold(
            appBar: new AppBar(),
            body: GridView.count(
              controller: _scrollController,
              scrollDirection: Axis.vertical,
              crossAxisCount: 2,
              mainAxisSpacing: 10.0,

              physics: const AlwaysScrollableScrollPhysics(),
              children: dataList.map((value) {
                return Container(
                      alignment: Alignment.center,
                      height: MediaQuery.of(context).size.height * 0.2,
                      margin: EdgeInsets.only(left: 10.0, right: 10.0),
                      decoration: BoxDecoration(
                        border: Border.all(color: Colors.black),
                      ),
                      child: Text("Item ${value}"),
                    );


              }).toList(),
            )));
  }

  //// ADDING THE SCROLL LISTINER
  _scrollListener() {
    if (_scrollController.offset >=
            _scrollController.position.maxScrollExtent &&
        !_scrollController.position.outOfRange) {
      setState(() {
        print("comes to bottom $isLoading");
        isLoading = true;

        if (isLoading) {
          print("RUNNING LOAD MORE");

          pageCount = pageCount + 1;

          addItemIntoLisT(pageCount);
        }
      });
    }
  }

  ////ADDING DATA INTO ARRAYLIST
  void addItemIntoLisT(var pageCount) {
    for (int i = (pageCount * 10) - 10; i < pageCount * 10; i++) {
      dataList.add(i);
      isLoading = false;
    }
  }

  @override
  void dispose() {
    _scrollController.dispose();
    super.dispose();
  }
}

上述程序的输出如下

And output of the above program as follow

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